The car has a mass of 1200 kg

Question

1) The same car reaches a top speed of 15 m/s, then begins braking. It comes to a halt in 20 seconds. Draw a free body diagram of the car and find the force of friction (magnitude and direction) that the road makes on the wheels now.

2) The same car is now towing a 200kg trailer. It accelerates out of the stoplight a little slower, at 0.8 m/s2. Draw free-body diagrams of the car and the trailer as it accelerates. What is the force of friction that the road makes on the car wheels now?

Answer 1

Both forces of friction point to the left, since their effect is to make the car stop.

For more details, see the links below:

Friction problem 1 body diagrams and force value:

desmos.com_calculator_iqv85dynuj

Friction problem 2 body diagrams and force value:

desmos.com_calculator_gyspoafyxf

Replace the _ with /.